The proposed research focuses on the central problem of cognition for all species and ages--how new information is integrated with old. This problem underlies both the elaboration of the knowledge base and the remediation of learning and memory deficits in individuals who are cognitively impaired. We propose that the solution to the "central problem" is encapsulated in the construct of the time window. These experiments will examine this solution, the factors that affect it, and their consequences for what can be learned and how long it can be remembered. Preverbal infants are ideally suited for research on time windows because they lack extensive experience, are not subject to linguistic influence, their exposure to critical stimuli can be rigorously controlled, and their forgetting functions have been systematically documented. Time windows are also particularly amenable to study with infants because the fundamental mechanisms of memory processing do not change with age, but the temporal parameters of memory processing change dramatically. Moreover, these changes are experiential, not maturational: Given more retrieval experience, for example, the memory processing of younger infants becomes like that of older ones. We recently determined the mechanism by which events within a time window are integrated: Infants covertly associated 2 physically absent events that had never co-occurred but whose memory representations merely "came to mind" or were activated simultaneously. The implications of this finding are profound. We will characterize the time windows for the formation, maintenance, and updating of latent associations and for extinction. We will also examine 2 factors that affect time windows (number of retrievals, retrieval difficulty) and the nature of their effects. From a mental health vantage, this research will inform clinicians and other practitioners how to introduce new information so that it can be acquired most efficiently and remembered longest, how to manage or eliminate undesirable behavior, and how to design personalized interventions to ameliorate learning and memory deficits in individuals of all ages, whether brain-damaged or not. From a theoretical vantage, this research will take a giant step toward solving the "central problem" by elucidating how and when the effects of experiences combine, endure, and contribute to the knowledge base. The research will also provide a unique and systematic database for neuroscientists seeking the biological underpinnings of learning and memory.